It has been proposed to transport telecommunications signals over a power line. International Patent Application WO 98/06188 A1 (Northern Telecom) describes such a network. Delivering a telecommunications service in this manner is attractive as it overcomes the need for installing cabling to each subscriber, which is one of the greatest costs in providing a new telecommunications network. Existing power lines are used to carry the telecommunications signals to subscribers.
Power line transmission is one of several ways for delivering communications to subscriber premises and is therefore sensitive to competition with existing copper wires and more recent alternatives such as optical fibre/coaxial cable delivery and fixed radio access techniques. Therefore, there is a desire to provide a system that is capable of delivering an acceptable quality of service at a cost that is attractive to a subscriber.
In the above-mentioned WO 98/06188 A1 communications signals are injected onto one or more of the power lines leading from an electricity substation at a position on the line near to the substation.